In recent years there has been an increasing number of surgeons using surgical staples, rather than conventional sutures. This is true because the use of surgical staples and surgical stapling instruments has made many difficult procedures much simpler. Of even more importance, however, is the fact that the use of surgical staples significantly reduces the time required for most procedures, and therefore reduces the length of time for which a patient must be maintained under anesthetic.
Many types of surgical stapling instruments have been developed for many different procedures. The present invention is directed to that type of surgical stapling instrument which has a cartridge and driver assembly and an anvil in opposed spaced relationship to the cartridge. Tissue to be joined is located between the cartridge and the anvil. The distance between the cartridge and the anvil is adjustable. When tissue to be joined is located between the cartridge and the anvil, and the distance therebetween is adjusted to be within the operational or working gap of the instrument, the driver can be actuated to drive the staple or staples from the cartridge, through the tissue to be joined, and against the anvil to form the staple or staples. The working gap of the instrument is that range of distances between the cartridge and the anvil within which proper forming of the staple is assured.
There are a number of such surgical stapling instruments. One non-limiting example of such a surgical stapling instrument is an intraluminal anastomosis surgical stapling instrument. U.S. Pat. No. 4,319,576 teaches an exemplary surgical stapling instrument of this type. Another non-limiting example of a surgical stapling instrument to which the teachings of the present invention are directed is a linear surgical stapling instrument. An example of such an instrument is taught in U.S. Pat. No. 4,527,724. A linear surgical stapling instrument is one in which a single actuation of the instrument implants and forms at least one rectilinear row of surgical staples. While not intended to be so limited, for purposes of an exemplary showing the present invention will be described in terms of its application to a linear surgical stapling instrument. Such an instrument is used on many different organs and tissues such as the lung, the esophagus, the stomach, the duodenum and throughout the intestinal track.
It is common for linear surgical stapling instruments of the type taught in the above identified copending application to be provided with cartridge and driver assemblies so configured that two linear rows of surgical staples are implanted when the instrument is actuated, one row being lngitudinally staggered with respect to the other. This requires a cartridge having two rows of forming pockets, each containing a surgical staple, and a driver having two rows of tines to provide a driver tine for each cartridge forming pocket. In their most usual configuration, each forming pocket is rectangular transverse cross section, with a groove at each end adapted to receive and frictionally retain the legs of a staple. Each driver tine is also rectangular in cross-section having considerable clearance in its respective forming pocket and being adapted to engage the crown portion of its respective staple between the legs thereof. This construction has certain drawbacks.
First of all, it is commonplace to make the cartridge and the driver of injection molded plastic material. Both structures are complex in configuration and require careful molding techniques. Since the driver tines have to be quite small to fit within the cartridge, it is difficult to make them of adequate strength. The transverse cross sectional configuration of the cartridge forming pockets is such that a staple could be loaded in the pocket in skewed fashion, as will be explained hereinafter. Furthermore, each driver tine engages its respective staple along the crown thereof between the staple legs, and not over the staple legs themselves which is most desirable. In some instances an improperly formed staple could have its crown re-enter its forming pocket, jamming into its driver or between the driver and the adjacent surface of its forming pocket.
The present invention is based upon the discovery that if the individual driver tines are configured to have a substantially biconvex cross-section and if the forming pockets in the cartridge are provided with corresponding biconvex shapes, the above noted deficiencies can be greatly reduced or eliminated. First of all, the strength of the individual driver tines is increased by increasing the width with respect to the length of the driver tine cross-section. Furthermore, when the driver tines and cartridge are made of plastic, the molding flow is improved. The possibility of improper staple loading is eliminated and the chances of jamming by an improperly formed staple is greatly reduced. There is better guidance of the staple and the driver tine in each cartridge forming pocket, and each driver tine engages its respective staple over the staple legs, where the driving force is most needed. Finally, both the driver and the cartridge have a better appearance. In addition, the substantially biconvex shape of the cartridge forming pockets allows the provision of more forming pockets in a given cartridge length and more staples in a given staple line, while maintaining strong cartridge construction, since there is more material between adjacent forming pockets than there would be with rectangular forming pockets.